"""Service layer for CoordWorkItem."""

from typing import Optional
from uuid import UUID

from fastapi import HTTPException, status
from sqlalchemy.orm import Session

from api.models.coord_work_item import CoordWorkItem
from api.models.coord_workflow import CoordWorkflow
from api.schemas.coord_work_item import CoordWorkItemCreate, CoordWorkItemUpdate


def get_work_items(
    db: Session,
    workflow_id: Optional[str] = None,
    project_key: Optional[str] = None,
    status_filter: Optional[str] = None,
    assigned_session: Optional[str] = None,
    skip: int = 0,
    limit: int = 100,
) -> tuple[list[CoordWorkItem], int]:
    """Return paginated work items with optional filters."""
    q = db.query(CoordWorkItem)
    if workflow_id:
        q = q.filter(CoordWorkItem.workflow_id == workflow_id)
    if project_key:
        q = q.filter(CoordWorkItem.project_key == project_key)
    if status_filter:
        q = q.filter(CoordWorkItem.status == status_filter)
    if assigned_session:
        q = q.filter(CoordWorkItem.assigned_session == assigned_session)
    total = q.count()
    items = q.order_by(CoordWorkItem.priority.desc(), CoordWorkItem.created_at.asc()).offset(skip).limit(limit).all()
    return items, total


def get_work_item_by_id(db: Session, item_id: UUID) -> CoordWorkItem:
    """Return a single work item or raise 404."""
    item = db.query(CoordWorkItem).filter(CoordWorkItem.id == str(item_id)).first()
    if not item:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail=f"Work item {item_id} not found"
        )
    return item


def create_work_item(db: Session, data: CoordWorkItemCreate) -> CoordWorkItem:
    """Create and persist a new work item, validating the parent workflow exists."""
    workflow = db.query(CoordWorkflow).filter(CoordWorkflow.id == data.workflow_id).first()
    if not workflow:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail=f"Workflow {data.workflow_id} not found"
        )
    try:
        item = CoordWorkItem(**data.model_dump())
        db.add(item)
        db.commit()
        db.refresh(item)
        return item
    except Exception as e:
        db.rollback()
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Failed to create work item: {e}"
        )


def update_work_item(db: Session, item_id: UUID, data: CoordWorkItemUpdate) -> CoordWorkItem:
    """Apply partial update to a work item."""
    item = get_work_item_by_id(db, item_id)
    try:
        for field, value in data.model_dump(exclude_unset=True).items():
            setattr(item, field, value)
        db.commit()
        db.refresh(item)
        return item
    except Exception as e:
        db.rollback()
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Failed to update work item: {e}"
        )


def delete_work_item(db: Session, item_id: UUID) -> dict:
    """Delete a work item by ID."""
    item = get_work_item_by_id(db, item_id)
    try:
        db.delete(item)
        db.commit()
        return {"message": "Work item deleted", "item_id": str(item_id)}
    except Exception as e:
        db.rollback()
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Failed to delete work item: {e}"
        )